1. Field of the Invention
The invention relates to a sewage treatment plant including clarifier and aerator chambers which promote sewage-degrading flow characteristics.
2. Description of the Related Art
Self-contained subterraneous sewage treatment apparatuses commonly are used in communities in which houses are not connected to centralized sewage systems. Typically, these apparatuses are constructed from concrete or fiberglass, cast as one part or formed from a number of parts. The apparatuses usually include a housing with walls that define internal aerator and clarifier chambers. The aerator chamber is the heart of the sewage treatment plant. Sewage received in the aerator chamber is oxygenated. Introduction of oxygen into the sewage intimately mixes the organic components of the sewage with the bacteria populations in the aerator chamber, creating an activated sludge. The bacteria reduce the organic components of the sewage. Additionally, to maximize the oxygen content of the sewage, the sewage must circulate in a manner that maintains organic components in suspension. If the organic components settle, they are not as accessible and less likely to be broken down by the bacteria.
Ideally, once the sewage is has been treated sufficiently, when the bacteria has broken down a target amount of the organic components in solution, the activated sludge passes from the aerator chamber into a clarifier chamber. In the clarifier chamber, any solids remaining in suspension which have not been broken down settle and are returned to the aerator chamber for continued circulation and breakdown. The activated sludge is treated in the clarifier chamber then voided out of the clarifier chamber to be absorbed by the environment.
The key to consistent, efficient, and reliable sewage treatment is assuring that the proper amount of oxygen is introduced into the sewage for reaction with the bacteria. The speed at which reduction of the organic components in the sewage is accomplished is directly related to the amount of oxygen that can be introduced into the sewage. The rate of oxygen introduction is directly related to the configuration of, and the diffusion mechanisms used to introduce oxygen in the aerator chamber. Proper configuration of the aerator chamber and placement of the diffusers therein is crucial. Once an appropriate configuration is selected, oxygen content enhancement of the sewage may be increased by increasing the flow of the sewage within the chamber, perhaps with turbulent characteristics. The oxygen content also may be enhanced by maintaining oxygen at a high pressure in association with the sewage, similar to carbonating a beverage.
The patent literature is replete with many sewage treatment apparatuses; however, none provide for enhancing sewage flow, nor associating gas at super-ambient pressure with sewage. For example, U.S. Pat. No. 2,987,186, issued Jun. 6, 1961, to David W. Burgoon et al., describes an apparatus for treating waste materials. The apparatus includes a tank with a vertical wall that defines side-by-side aerating and clarifying chambers. A diffuser is centrally located in the aerating chamber. Activated sludge from the aerating chamber passes into the clarifying chamber via an aperture in a vertical wall. Particulate matter remaining in solution precipitates from solution and flows back into the aerating chamber via a conduit at the bottom of the vertical wall. The conduit has an outlet proximate to the diffuser. The clarified sewage passes out of the clarifying chamber by an exit conduit and into the environment.
U.S. Pat. No. 3,195,727, issued Jul. 20, 1965, to Gary W. Kibbee, describes a waste products treatment apparatus having floating solid feedback structure. The device has laterally-disposed aerating and clarifying chambers. The clarifier chamber does not extend all the way to the bottom of the tank. An angled wall between the aerator chamber and the clarifier chamber projects into the outer wall of the clarifying chamber, above the bottom of the tank. A passageway between the angled wall and the outer wall permits particulate matter in suspension to return to the aerating chamber. The clarifier chamber also includes a baffle for trapping large particulate matter. On the other side of the baffle is a clarified liquid basin. Clarified sludge is voided from the clarified liquid basin into the environment.
U.S. Pat. No. 3,206,032, issued Sep. 14, 1965, to Mark C. Nottingham et al., describes a sewage disposal tank. The apparatus includes a tank, defining three serial chambers. The first chamber includes a number of diffusers which introduce oxygen into and circulate the sludge. Oxygenated sludge from the first chamber passes into the second chamber after having passed through a baffle that filters out large particulate matter. The second chamber includes a centrally-and bottomly-disposed foraminous member for screening sewage introduced into the second chamber. Some of the screened sewage is returned to a pump and urged through the diffusers along with ambient air. The second chamber is in fluid communication with the third chamber via a weir located near the surface of the sewage. Lighter, clarified sewage is conducted into the third chamber, a holding chamber. The sewage from the third chamber is voided into the environment.
U.S. Pat. No. 3,805,957, issued Apr. 23, 1974, to Robert R. Oldham et al., describes a floating solids return device. The device includes a tank having three serial chambers. Sewage is introduced into the first chamber and allowed to settle. Sewage flows into the secondary chamber through a weir located near the surface of the sewage. The second chamber includes a diffuser which introduces air into the sewage. Sewage flows from the second chamber into the third chamber through another weir located proximate to the sewage surface. The third chamber has an angled outer wall and a vertical wall separating the third chamber from the second chamber. The angled and vertical walls intersect above the bottom of the second chamber. The vertical wall has a passageway between the second and third chambers permitting solid particulate matter to be returned into the second chamber. Treated sewage is voided from the third chamber via another weir.
U.S. Pat. No. 3,951,817, issued Apr. 20, 1976, to John R. Snyder, describes a sewage treatment tank and tube settler. The device includes a diffuser located in the middle of and near the sewage surface of an aerating chamber. Material from the aerating chamber passes through a lower passage between the aerating chamber and a clarifying chamber, rather than through the weir located at the surface. The device also includes a weir located at the surface between the aerating chamber and the clarifying chamber.
U.S. Pat. No. 4,859,325, issued Aug. 22, 1989, to Murphy Cormier, describes a waste material treatment apparatus. The apparatus includes a tank having two serial chambers. The first chamber is an aerating chamber including a diffuser. The diffuser introduces oxygen into the aerating chamber which cooperates with baffles in the chamber to induce a predetermined circulation of the sewage. The clarifying chamber receives sewage from the aeration chamber via a passageway between the vertical wall separating the two chambers and the angled wall defining the clarification chamber. Sewage from the clarification chamber passes into the environment through a weir located near the sewage surface in the clarification chamber.
U.S. Pat. No. 5,162,083, issued Nov. 10, 1992, to Lee W. Forbes et al., describes an individual home waste water treatment plant conversion apparatus. The apparatus includes a circular tank with diffusers circumferentially dispersed about the lower periphery of the tank. A clarifier insert depends centrally from the ceiling of the tank. The clarifier insert has a horizontal cross-sectional profile that is generally oval in shape. The insert is vertically tapered from top to bottom and has a lower aperture located at a predetermined distance above the bottom of the tank. The clarifier insert defines an internal clarifier chamber surrounded by an aerator chamber. Sewage is introduced into the aerator chamber and circulated by the release of air by the diffuser members. Oxygenated sewage passes from the aerator chamber into the clarifier chamber through the lower aperture of the insert member. Particulate matter remaining in solution settles on the inner surface of the insert member and returns to the aerator chamber. Fluid is voided from the clarifier chamber through a weir located near the sewage surface at the top of the clarifier chamber.
None of the foregoing inventions are seen as teaching or suggesting the claimed sewage treatment method or apparatus therefor. None of the inventions uses cooperating walls of an aerator chamber to define interacting aerator zones that promote a sewage flow which enhances the oxygen content of the sewage. Also, none of the inventions associates oxygen at super-ambient pressure with sewage which enhances sewage oxygenation.